The middle-aged OS is not expected to die any time soon, just slowly fade away

In a twist of irony, the Unix platform celebrates its 40th birthday this year, as does the man whose work probably has done more to diminish the trendiness of Unix than anyone else: Linux founder Linus Torvalds.

Linux and Windows Server outsell Unix by volume. Indeed, given all the attention Windows and the open source Linux platform get, the battle for the mainstream server market can sometimes appear to be a duel between just these two platforms. Unix often seems like yesterday's -- or even last decade's -- news.

Unix remains a vital cog in enterprise IT and can be expected to remain so for years to come. Figures such as Oracle CEO Larry Ellison attest to its maturity. In a recent public appearance, Ellison endorsed both Linux and the Solaris Unix OS that Oracle wants to acquire as part of its planned $7.4 billion purchase of Sun Microsystems: "We are a supporter of Linux but Solaris is the more mature OS."

A Hewlett-Packard official chimes in that Unix would have a long life similar to how mainframes have continued to thrive. "I haven't seen mainframes [go] away and people were predicting their demise, what, 10, 20 years ago," says Brian Cox, director of software planning and marketing in the HP business-critical systems group. One reason: Unix offers deep integration and higher quality of service, says Satya Sharma, CTO for IBM's AIX-based Power systems.

Unix: A stable but consolidating marketA sampling of Gartner server shipment numbers does show Unix trailing Linux and Windows Server, as the chart below shows. (If the chart is not visible, you can see it in the original story at InfoWorld.com.)

Unix shipments went from 670,458 units shipped in 2006 to 437,414 units in 2009, with a slight uptick to 451,593 units anticipated in 2012. Linux server shipments for those same years read like this: 1,911,906 units in 2006, 1,682,633 units in 2009, and 1,980,532 units in 2012. Windows Server shipments total 5,416,453 units in 2006, 4,947,891 units in 2009, and 5,699,810 units in 2012. (The marketplace as a whole suffered from the current recession, thus the down numbers for all platforms.) For 2014, Gartner projects Linux shipments of 2,174,334 units, Windows shipments of 6,313,292, and Unix shipments of 474,993.

A user of all three platforms vouches for the maturity of Unix. "It's really at the core of every one of our enterprise systems," says Paul Sikora, vice president of IT transformation at the University of Pittsburgh Medical Center, which runs Unix for its Oracle and cache databases. Unix offers mature redundancy and clustering capabilities, and software vendors are comfortable with their software running on Oracle and Unix, Sikora says.

For example, Unix has been deployed for tougher workloads than Linux and Windows, HP's Cox says: "Unix really has been for what we call the much more demanding kinds of workloads, where you're looking at needing to have data warehouses which go to tens of terabytes." Unix also is the choice for banks, manufacturers, and telecommunications companies running millions of transactions per minute, he adds, because Linux and Windows Server lack the uptime levels needed for such jobs.

That's why major Unix providers such as IBM and HP continue to see growth in Unix sales. "Unix and [its IBM-specific derivative] AIX is definitely a growth business for IBM," says Sharma. IBM has grown its share of the Unix market from 19 percent in 2001 to 38 percent in 2009 in a stable market, he says. Sharma notes the total Unix market for all vendors is still an $18 billion per year for business worldwide, "which is nothing to sneeze at."

HP too is experiencing growth in Unix. "We're seeing growth -- maybe not the double-digit levels that we had seen back in the '90s, but it's still a strong, very stable business," Cox says. The growth at IBM and HP masks the fact that the overall Unix has been fairly static, meaning their growth is at the expense of other providers.

The new Linux and Windows Server kids are where the action isBut both IBM and HP have jumped into the Linux market. Despite HP's 26-year history with Unix and its HP-UX derivative and the company's claim to fame of being the first to sell Unix commercially to several markets, HP has switched from selling Unix systems based on its PA-RISC architecture to selling HP-UX on Intel Itanium systems, Cox concedes.

And Big Blue offers Linux on its Power servers. "It is true that Linux represents a significant growth in the server industry," Sharma notes.

"We love Linux," Cox says. "We make lots of contributions to the open source community. We love Windows as well." But Windows and Linux are like younger brothers to Unix, Cox notes, and can't handle some of the tasks that the more mature Unix can.

For example, Windows has been popular for e-mail, print and file-sharing services, and basic applications, Cox says. And Linux is popular for edge-of-the-network computing, for running systems such as firewalls and proxy servers, and for software development, he notes.

Although many still consider Unix the best option for high-demand applications, the technical differences between Linux and Unix are "going to be pretty minimal" going forward, argues Gartner analyst George Weiss. He expects that Linux will exploit hardware features such as better internal multitasking and multiprocessing. Plus, Linux runs on less-expensive x86 hardware than Unix and offers more application independence for programs available for x86 systems. The virtualization trend also leverages cheaper x86 boxes that are not the domain of Unix, he adds. That's why Weiss says Linux and Windows represent the two growth OSes.

"Unix will continue to have a footprint in the enterprise for a reasonable period of time, but increasingly, corporations are turning to Linux to run their enterprise systems," says Jim Zemlin, foundation executive director of the Linux Forum. In about a decade, however, the world will be "primarily made up of Windows and Linux," he predicts.

Sun's attempt to compete against Linux with an open source Unix-based Solaris derivative came too late, Weiss says. Many of his clients have already chosen Linux, leaving Solaris to its existing loyal base of users, which he does not expect to grow. In fact, some observers expect Solaris -- like any Unix version -- to decline in usage fairly soon.

Unix, though, will be around for a long time, Weiss says: "There will be a long tail of viability in Unix, even if one could prove that the same application that you're running on Unix could run on Linux just as well. Forty years of Unix is hard to trash in the mindset of many users." Still, he does expect a long-term decline for Unix.